1. Field of the Invention
The invention is a process for the isolation or purification of essentially methyl branched saturated C.sub.14 -C.sub.24 fatty acids from hydrogenated industrial fatty acid mixtures. The industrial fatty acid mixtures contain methyl branched saturated C.sub.14 -C.sub.24 fatty acids saturated or unsaturated straight chain C.sub.10 -C.sub.24 fatty acids as well as methyl branched unsaturated C.sub.14 -C.sub.24 fatty acids. The industrial fatty acid mixtures are catalytically hydrogenated and the essentially methyl branched saturated C.sub.14 -C.sub.24 fatty acids, contained in the hydrogenated fatty acid mixture, are separated from the saturated straight chain C.sub.10 -C.sub.24 fatty acids. The methyl branched C.sub.14 -C.sub.24 fatty acids can be further purified by known processes such as by distillation.
2. Statement of Related Art
Methyl branched, saturated and unsaturated C.sub.10 -C.sub.24 fatty acids occur as a by-product in the thermal or catalytic dimerization of the corresponding unsaturated straight chain fatty acids. The structure of the "so-called" isostearic acids formed in the dimerization of tall oil fatty acids has been described, cf. J. Am. Oil Chem. Soc. (1979), Vol. 56, pp. 823A-827A; ibid. (1974), Vol. 51, pp. 522-527; ibid. (1985), Vol. 62, 888-891.
Isostearic acids are liquid at ambient temperature and resistant to oxidation due to their saturated nature. They are therefore useful products, particularly in the formulation of lubricants and as components of cosmetic preparations and textile treatment agents. Several processes for the isolation and purification of isostearic acids from fatty acid mixtures obtained during the dimerization of fatty acids have been described. U.S. Pat. No. 2,812,342, for example, discloses a process according to which the industrial fatty acid mixtures, produced during the dimerization of C.sub.18 a fatty acids, are hydrogenated with known nickel catalysts and hydrogen under pressure and the isostearic acids obtained are isolated according to a process disclosed in U.S. Pat. No. 2,293,676, namely by dissolving in a suitable solvent and crystallizing out at reduced temperatures.